Is Emily Blunt Black Widow in the Iron Man?

I was under the impression that, ever since Goldeneye, a rule had been in place that every agile, over-sexualized Russian villainess character had to be played by Famke Janssen, but apparently I was way off on that, because Variety is reporting that Emily Blunt is up for the role of Black Widow in Iron Man 2:

With Mickey Rourke and Sam Rockwell negotiating to play key villains in "Iron Man 2," Marvel Entertainment and director Jon Favreau are now looking for the right thesp to play femme fatale Black Widow, another nemesis for Robert Downey Jr.'s Tony Stark.

Emily Blunt has emerged as the frontrunner to play Natasha Romanoff in the "Iron Man" sequel. She's a Soviet superspy who doubles as Black Widow, a beauty in a skintight black costume enhanced by high-tech weaponry.

Perhaps the Famke Janssen casting rule has been overruled by the obscure "One House on Haunted Hill, one Deep Rising, and one I-Spy and you're out!" ruling. Or maybe there's a dominant rule that one is only allowed to play one artificially-red-haired, skin-tight black jumpsuit-wearing superhero. Because Hollywood operates based on a complicated series of oblique trumps and overtrumps, much like a game of Magic: The Gathering.